Endomycopsis montevidensis n. sp.

A new species of the genusEndomycopsis is proposed. It was isolated from waste water, at Montevideo-Uruguay.By its morphological and biochemical proprieties it differs from allEndomycopsis previously described.

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Este trabajo fue desarrollado en el Laboratorio de Micologia de la Facultad de Química de Montevideo, Uruguay y en uso de una beca de la Universidad Federal de Pernambuco para perfecciobamiento en el estudio de las levaduras.     

Phytochrome-mediated responses of cells and protoplasts of green calli obtained from the leaves of a CAM plant

Green callus obtained from leaves of the CAM-inducible plant Kalanchoe blossfeldiana cv. Montezuma has previously been shown to perform C₃-type photosynthesis under 16-h days and to shift to crassulacean acid metabolism (CAM) under 9-h days. The utilization of photoperiodic regimes (i.e. night interruptions by 30 min red light) established that CAM induction in the callus was under the control of phytochrome, as shown by measurements of CAM criteria: phosphoenolpyruvate carboxylase activity and malic acid pools. Short-term responsiveness of the callus cells to phytochrome modulations by monochromatic radiations was also established by the rapid changes observed in the diameter of the callus-derived protoplasts. These results provide further evidence that whole plant correlations are not necessary for phytochrome operativity.Abbreviations CAM crassulacean acid metabolism - PAL phenylalanine ammonia lyase (EC 4.3.1.5) - PAR photosynthetically active radiations - PEPC phosphoenolpyruvate carboxylase (EC 4.1.1. 31) - Rubisco ribulose 1,5 bisphosphate carboxylase (EC 4.1.1.39)     

Role of cell-mediated immunity in the resistance to experimental sporotrichosis in mice

The in vitro activity of several new imidazoles, cloconazole, sulconazole, butoconazole, isoconazole and fenticonazole, were compared with those of amphothericin B, flucytosine, and three azoles: econazole, miconazole and ketoconazole against isolates of pathogenic Candida. A total of 186 clinical isolates of 10 species of the genus Candida and two culture collection strains were tested by an agar-dilution technique. Isoconazole was the most active azole, followed by butoconazole and sulconazole. Differences between some of the species in their susceptibility to the antifungal agents were noted. Sulconazole and cloconazole had the highest activity in vitro against 106 isolates of C. albicans. Butoconazole and isoconazole were also very active against isolates of C. albicans, and were the most active azole compounds against 80 isolates of Candida spp.     

Endomycopsis montevidensis n. sp.

A new species of the genusEndomycopsis is proposed. It was isolated from wast water, at Montevideo-Uruguay.By its morphological and biochemical proprieties it differs from allEndomycopsis previously described.Este trabajo fue desarrollado en el Laboratorio de Micologia de la Facultad de Quimica de Montevideo, Uruguay y en uso de una beca de la Universidad Federal de Pernambuco para perfeccio bamiento en el estudo de las levaduras.     

The effect of the plating medium on the recovery of nonsense suppressors in Saccharomyces cerevisiae

The recovery of nonsense suppressors in a strain of Saccharomyces cerevisiae carrying five ochre mutations, tr, hi, ly, ar, and ad, is affected by the plating medium. The highest frequency is observed on tryptophanless medium, while the lowest is observed on adenineless medium. Experiments showed that exogenous histidine inhibits suppressor expression and that exogenous adenine relieves this inhibition. In histidine-independent strains, mutation expression requires adenine. A model, based on the role of RNA in supersuppression and on the biosynthetic pathways of histidine and adenine, is proposed to account for the observed data. It cannot, however, account for the high frequency of suppressors on tryptophanless medium. The tentative conclusion is drawn either that mis-reading of the tryptophan nonsense codon by mutated tRNA is facilitated by the neighboring bases or that the type of acceptable amino acid is less rigorously limited in the mutated site of the tryptophan locus than in those of the other suppressible loci.This work was in part supported by the Calouste Gulbenkian Foundation and by the Medical Research Council (Grant No. G969/24/B).     

DETERMINATION OF GUSTATORY SUCROSE THRESHOLD IN WATER BY USE OF A LINEAR SUCROSE GRADIENT

A novel experimental method was developed which allows the determination of the threshold concentration of sucrose by use of a linear sucrose gradient in water. With this method a continuous tasting of the test-liquid is possible. A panel of 15 persons experienced in taste-testing was used. Three gradients of different steepness were applied: 0 to 1.5% (w/w) sucrose in 2 min (I), 3 min (II) and 4 min (III). The results of the new method were compared with those of the standard method (DIN). With gradients I and II we found values which were significantly higher than those of the standard method (I: 0.49% (w/w); II: 0.46% (w/w); DIN: 0.31% (w/w)), whereas with gradient III the same threshold value was found as with the DIN-Method (III: 0.32% (w/w)).     

Trophic ecology of three stingrays (Myliobatoidei: Dasyatidae) off the Brazilian north-eastern coast: Habitat use and resource partitioning

Understanding the ecological role of species with overlapping distributions is central to inform ecosystem management. Here we describe the diet, trophic level and habitat use of three sympatric stingrays, Hypanus guttatus, H. marianae and H. berthalutzae, through combined stomach content and stable isotope (δ¹³C and δ¹⁵N) analyses. Our integrated approach revealed that H. guttatus is a mesopredator that feeds on a diverse diet of benthic and epibenthic marine and estuarine organisms, principally bivalve molluscs, Alpheus shrimp and teleost fishes. Isotopic data supported movement of this species between marine and estuarine environments. H. berthalutzae is also a marine generalist feeder, but feeds primarily on teleost fishes and cephalopods, and consequently occupies a higher trophic level. In contrast, H. marianae is a mesopredator specialized on shrimps and polychaetas occurring only in the marine environment and occupying a low niche breadth. While niche overlap occurred, the three stingrays utilized the same prey resources at different rates and occupied distinct trophic niches, potentially limiting competition for resources and promoting coexistence. These combined data demonstrate that these three mesopredators perform different ecological roles in the ecosystems they occupy, limiting functional redundancy.     

Testing an Adaptive Hypothesis Through Context-Dependence: Effects of Water Depth on Foraging Behaviour in Three Species of Garter Snakes

Adaptive hypotheses based on interspecific comparisons can be tested by evaluating the context‐dependence of the behaviour of individual organisms. Drummond (Behaviour, 86, 1983, 1) categorized garter snake species (Thamnophis) as terrestrial–aquatic generalists or aquatic specialists based on diet and aquatic foraging behaviour. He hypothesized that the characteristic foraging behaviours of aquatic specialists – including frequent crawling on the underwater substrate and a high rate of underwater predatory strikes – are adaptations for feeding on relatively widely dispersed aquatic prey. Drummond's hypothesis based on interspecific comparisons suggests that individual snakes might change their foraging in the direction of aquatic specialist behaviour with an increase in water depth (which increases prey dispersion). I tested this prediction through laboratory observations of Mexican Pacific lowlands garter snakes (T. validus) feeding on minnows in shallow (2 cm) and deep (3–7 cm) water. Members of this species are appropriate subjects because they are ecologically intermediate between the generalists and aquatic specialists studied by Drummond, and thus might be expected to show more variation in aquatic foraging behaviour than those species. T. validus showed significantly higher frequencies of crawling on the underwater substrate and of underwater strikes in the deep water than in the shallow water; i.e. increased water depth shifted the behaviour of these snakes toward that of aquatic specialists, thus supporting Drummond's hypothesis. Individuals of an aquatic specialist species, the narrow‐headed garter snake (T. rufipunctatus), showed less pronounced changes in behaviour with increased water depth. Western ribbon snakes (T. proximus), which feed primarily at the land–water interface (and are expected to act like terrestrial–aquatic generalists), typically refused to feed in deep water. Interspecific differences in underwater visual acuity may underly the behavioural differences among the three species by determining whether changes in foraging behaviour with water depth are advantageous. Information on phylogenetic relationships suggests that the facultative behaviour of T. validus may represent an intermediate stage in the evolution of aquatic specialization.